The present invention relates generally to a conveying apparatus, annd more particularly to an apparatus for conveying particulate material. Still more particularly the invention relates to an apparatus for conveying particulate material which are of such type that they will pass on mechanical energy transmitted to them in forward direction with minimum loss.
Certain materials, for instance metal cuttings which originate in chip-removing machine tools, can be conveyed by subjecting them to energy which causes a certain amount of compression but which is then not further dissipated. In other words, after undergoing a certain amount of compression, such material will then advance (in the direction in which the energy acts) essentially in the manner of a solid body, without energy losses. Another type of material meeting this qualification is sludge which, just like a liquid, tends to convey energy transmitted to it in all directions but has a preferred energy transmission direction in a forward sense, that is in the direction in which the energy acts.
Other materials, for which the apparatus according to the present invention is not suitable and which are mentioned herein in order to make a clear distinction, include for example sand. If sand has energy supplied to it, in the sense of pressure trying to urge it in certain in a the sand will become compressed but will thereafter not pass on the energy in the direction in which it acts, but instead will become increasingly compacted.
With this in mind it is pointed out that the prior art has long known screw conveyors utilizing a pipe in which a worm screw rotates. The interior surface of the pipe is usually so profiled that the material conveyed by the screw is prevented from rotating with the latter in the pipe, and is constrained largely to advance only in the direction of rotation of the pipe. That is, the screw rotates with reference to the pipe as well as with reference to the materials being conveyed. This causes the material to slide forwardly through the pipe within the slides of the screw thread and thereby to be conveyed. A problem with conventional screw conveyors is that the screw must extend over substantially the entire length of the pipe through which material is to be conveyed by it, because the screw produces only minimal compression of the material being conveyed and must therefore be present at all points at which a conveying action is required. Of course, there are many instances in which it is possible to install, the result being that the application of screw conveyors is strictly limited by this factor.